1. Field of the Invention
The present invention relates to a monitor display control apparatus and a monitor display control method in which a map image is displayed on a display screen of a monitor component such as a car navigation device loaded on a vehicle, or the like.
2. Description of the Related Art
There are automobiles in which a car navigation system is installed. The car navigation system has a monitor component, and a map image or the like can be displayed on a display screen of the monitor component. Further, when a map image is being displayed on the display screen of the monitor component, a cursor is displayed on the center of the display screen. In this case, the map image is made to move (scroll) relatively with respect to the cursor in accordance with input from an operation component.
As such a car navigation system, there is a car navigation system in which a relative moving speed (scrolling speed) of a map image with respect to a cursor can be varied in plural stages in order to rapidly find out a destination or the like.
For example, there is a car navigation system in which a scroll key for scrolling a map image on a display screen is provided, and there is disclosed one example thereof in Japanese Patent Application Laid-Open (JP-A) No. 8-69515. This system is structured such that a scale factor of the map image displayed on the display screen is varied in stages and automatically in predetermined time units while maintaining a scrolling speed to be constant when a time of continuous thrusting the scroll key is increasing.
Moreover, in this system, when a destination has been registered in advance, the scale factor of the map image is varied so as to be approximate to an original scale (maximum enlarged display) as the destination approaches the cursor on the display screen. Namely, when the destination approaches the cursor on the display screen, the map image is displayed to be enlarged in spite of a time of continuous thrusting the scroll key, and the contents of the map image are reported in detail.
However, even when the destination has approached the cursor on the display screen, when the destination has not been registered in advance, the scale factor of the map image is not varied to an original scale (maximum enlarged display), and there are cases in which the map image is displayed in a wide range (displayed to be reduced). In such a case, it is necessary to interrupt thrusting the scroll key once, and to display the destination and the vicinity of the destination to be enlarged due to the scale factor of the map image being returned to the current scale. Namely, scrolling of the map image must be once interrupted in order to obtain the detailed information on the destination and the vicinity of the destination. As a result, an operation in which thrusting of the scroll key is interrupted and the scroll key is thrust again is required, and there is the disadvantage that the operation of the scroll key is made to be troublesome, and the ease of operation of scrolling a background image has been poor.
Further, there is a car navigation system in which, when a joy stick key provided to a remote controller for inputting various indications is tilted relatively from the reference position thereof for a long time, the scrolling speed is accelerated and only the road information highly necessary for a driver is displayed on a display screen of a monitor component, and there is disclosed one example thereof in JP-A No. 8-219803.
However, from the time when the joy stick key is tilted to the time when a predetermined time passes, the scrolling speed of the map image is not accelerated, it is difficult to instantly vary the scrolling speed of the map image (for example, to accelerate the scrolling speed) with an intention of the operator being reflected. Further, because this system is not structured such that a scrolling speed of the map image is limited to an extent in which the contents of the map image can be grasped when the scrolling speed is accelerated, there are cases in which the driver cannot visually recognize the map image when the scrolling speed is made fast. Moreover, because this system has a structure in which the map image cannot be displayed in a wide range (a structure in which the scale factor of the map image is made to be constant), a region which does not include a destination and the vicinity of the destination is made to be on an original scale (is displayed to be enlarged). As a result, there is the disadvantage that, even when the driver wishes to display the map image in a wide range, the system cannot correspond thereto, and the ease of operation of scrolling a background image has been poor.
Moreover, there is a car navigation system in which, when an operation of a shift key of the remote controller is carried out in a state in which an operation of the joy stick provided to the remote controller is continued, a scale factor of the map image displayed on the monitor component is varied only during the time when the operation of the shift key is being carried out, and there is disclosed one example thereof in JP-A No. 2002-81942. In this system, when the operation of the shift key is interrupted, the scale factor of the map image is automatically returned to the scale factor before the operation of the joystick was started. In this way, this system can momentarily vary the scale factor of the map image displayed on the display screen of the monitor component.
However, when an attempt is made to return the display from being in a wide-range display to being on an original scale (enlarged display), the operation of the joystick must be interrupted, i.e., the scrolling of the map image must be once stopped. In this way, in this system, because scrolling of the map image cannot be smoothly carried out, it cannot be necessarily said that the ease of operation of scrolling the map image is excellent.